Approaches for establishing connections in an overloaded communication network are known, in particular, from private communication networks.
The invention is based on a conventional method for establishing a connection, as used with private branch exchange networks, for example with internal company networks which have several network access points to a public telephone network. This method is described, for example, in the article "Network TK Installations without Limits", by Hilmar Dehlen, NTZ, Vol. 45 (1992), No. 9 on pages 714 to 720.
The private communication network is formed by several private branch exchanges interconnected via direct routes. Each of the individual private branch exchanges have network access to the public telephone network. When a private branch exchange receives a call request requesting a connection to a terminal of a different private branch exchange of the private network, and if a bottleneck exists in the private network for establishing the requested connection via links of the private network, then there is an automatic overflow into the public telephone network, i.e. the call request is routed onward from the private branch exchange to the public telephone network, and a connection to the requested terminal is established via the public telephone network.
This method for establishing a connection has the disadvantage that significant expenses are incurred in an overloaded situation, since the public telephone network has to be used without the possibility to achieve a more uniform utilization of the private communication network.